Stagnant Supercivilizations and Interstellar Travel

byPaul GilsteronJuly 28, 2017

Just how long can a civilization live? It’s a key question, showing up as a factor in the Drake Equation and possibly explaining our lack of success at finding evidence for ETI. But as Andrei Kardashev believed, it is possible that civilizations can live for aeons, curbed only by the resources available to them, opening up the question of how they evolve. In today’s essay, Nick Nielsen looks at long-lived societies, asking whether they would tend toward stasis — Clarke’s The City and the Stars comes to mind — and how the capability of interstellar flight plays into their choices for growth. Would we be aware of them if they were out there? Have a look at supercivilizations, their possible trajectories of development, and consider what such interstellar stagnation might look like to a young and questing species searching for answers.

by J. N. Nielsen

What are stagnant supercivilizations?

As far as I know there are no precise definitions of supercivilizations, but this should not surprise us as there are no precise definitions of civilization simpliciter. In his paper, “On the Inevitability and the Possible Structures of Supercivilizations” (1985), Nikolai S. Kardashev explicitly formulated two assumptions regarding supercivilizations:

“I. The scales of activity of any civilization are restricted only by natural and scientific factors. This assertion implies that all processes observed in Nature (from phenomena in the microcosmos to those in the macrocosmos and all the way to the whole Universe) may in time be utilized by civilizations, be reproduced or even somewhat changed, though of course always in accordance with the laws of Nature.

“II. Civilizations have no inner, inherent limitations on the scales of their activities. This implies that presumptions of a possible self destruction of a civilization, or of a certain restrictions on the level of its development are not factual. Actually social conflicts may in fact be resolved, while civilizations will always face problems that demand larger scales of activity.” [1]

If Kardashev was right, there being only natural and scientific restrictions on the scale of the activity of civilization, and the absence of inherent limitations on civilizations, would mean that an expanding civilization would just keep expanding, subject only to natural laws like those of general relativity and quantum theory, thermodynamics and conservation laws. Presumably, then, older expanding civilizations would eventually become supercivilizations in virtue of the scale of their activities, which would grow proportionally (or perhaps exponentially) to their age. Here we see the relationship between supercivilizations and the recurrent motif of million-year-old or even billion-year-old civilizations. But once grown to these dimensions, what then?

This seems to contradict Kardashev’s second assumption, that, “Civilizations have no inner, inherent limitations on the scales of their activities,” but the carrying capacity of the cosmos would constitute an extrinsic or exogenous limitation on the scales of a supercivilization’s activities, rather than an intrinsic or endogenous limitation. Moreover, this extrinsic limitation, which, once encountered, entails stagnation, is consistent with Kardashev’s first assumption, that a supercivilization’s activities must be, “in accordance with the laws of Nature” and are restricted by natural factors. The carrying capacity of the cosmos is the natural restriction upon the growth of supercivilizations.

If a galaxy is the ecosystem in which a supercivilization comes to maturity, then the carrying capacity of a galaxy will determine the growth and eventual stagnation of supercivilizations once carrying capacity is reached, with that carrying capacity being determined by the accessibility of available matter and usable energy at the disposal of a supercivilization. This ecological limit to the growth of supercivilizations would constitute, “natural and scientific factors,” that would restrict a supercivilization’s scale of activity, constituting a confirmation of Kardashev’s principles, and would, additionally, make the metaphor of galactic ecology literally true.

This is but one possible scenario for the stagnation of a supercivilization. Sagan and Newman suggested a scenario of supercivilization stagnation based upon the intelligent progenitor species of a civilization transcending their biological limitations and becoming effectively immortal:

“A society of immortals must practice more stringent population control than a society of mortals. In addition, whatever its other charms, interstellar spaceflight must pose more serious hazards than residence on the home planet. To the extent that such predispositions are inherited, natural selection would tend in such a world to eliminate those individuals lacking a deep passion for the longest possible lifespans, assuming no initial differential replication.” [3]

According to Sagan and Newman the result of this would be:

“…a civilization with a profound commitment to stasis even on rather long cosmic time scales and a predisposition antithetical to interstellar colonization.” [4]

I could criticize this scenario on several grounds, but my purpose here is not to engage with the argument, but to present it for exhibition as one among multiple possible sources of stagnation for advanced civilizations. The point is that even the largest, oldest, most advanced civilizations are subject to stagnation—perhaps especially subject to stagnation.

[We could pursue terraforming within our own planetary system even without interstellar travel.]

Are there hard limits to interstellar travel?

In the argument that I unfolded in What Do Stagnant Supercivilizations Do During Their Million Year Lifespans? so as to concede a point to potential critics before this was used as a cudgel against my argument, I tried to show how, even without interstellar travel, a supercivilization could provide for itself civilizational-scale stimulation. My argument was that even a supercivilization confined to its home planetary system could engage in terraforming (or its non-terrestrial equivalent) and even world-building, and so might be able to observe the development of life over biological scales of time and the development of intelligence and civilization over their respective scales of time.

My assumption in making this argument was that a civilization in a position to make scientific observations of phenomena as fundamental as the origins of life, intelligence, and civilization, eventually would formulate a vast body of scientific knowledge based on these scientific observations. All of this was mere prelude in order to ask the question that was bothering me at the time: could a supercivilization remain stagnant when it was in a position to assimilate a vast body of scientific knowledge? It seems unlikely to me that a civilization that had grown to supercivilization status in virtue of its mastery of science and technology could remain unaffected by an influx of scientific knowledge.

As I noted above, I sought to demonstrate the possibility of civilizational-scale intellectual stimulation without recourse to interstellar space travel in order to focus on what is still possible to a very old civilization even under hard limits to space travel. If such a civilization also possessed technology sufficient for interstellar travel, then the possibilities for stimulation would be all the greater, and my argument would be strengthened, so that considering the narrower question of a supercivilization stranded within its home planetary system constituted a more rigorous test of the idea of civilizational-scale scientific stimulation.

We all know that, even among scientists, even among advocates of space travel, there are those who insist upon hard limits to interstellar travel. Hence the need to make an argument without an appeal to interstellar travel. This insistence upon hard limits to interstellar travel is not my position, but I do want to try to understand the reasoning and the motivations that have led otherwise intelligent individuals to declare interstellar travel to be not merely difficult, but an insuperable impossibility (or so difficult as to be impossible for all practical purposes). What, then, are the reasons given for the impossibility or impracticality of interstellar travel? I will consider this question by way of a digression discussing the idea of the search for extraterrestrial intelligence (SETI) and what I call the SETI paradigm.

What is the SETI Paradigm?

Among those who insist upon hard limits to interstellar travel are many advocates of SETI, which is usually conceived as searching for intelligent extraterrestrial signals, whether radio or optical or otherwise. The two positions—denial of the possibility of interstellar travel and pursuit of SETI—are tightly-coupled, as the unlikelihood of interstellar spacefaring civilization is used to argue for SETI as the only alternative to discovering other life and intelligence in the universe through space exploration.

Philip Morrison, who along with Giuseppe Cocconi wrote the first paper on the possibility of SETI, also held this view in regard to, “…real interstellar travel, where people, intelligent machines, or whatever you like, go out to colonize. You travel in space as Magellan circumnavigated the world. I do not think this will ever happen. It is very difficult to travel in space.” [5]

Perhaps the locus classicus of the SETI paradigm was to be found already in 1962, three years after the Cocconi and Morrison paper:

“…space travel, even in the most distant future, will be confined completely to our own planetary system, and a similar conclusion will hold for any other civilization, no matter how advanced it may be. The only means of communication between different civilizations thus seems to be electro-magnetic signals.” [6]

And here is another clear statement of the SETI paradigm:

“The bottom line of all this is quite simply that interstellar travel is so enormously expensive and/or perhaps hazardous, that advanced civilizations do not engage in the practice because of the ease of information transfer via interstellar communication links.” [7]

The frequency with which cautions regarding the danger of interstellar travel are employed as an argument against interstellar travel suggests that the class of persons writing against interstellar travel are risk averse, but that does not mean that all sectors of society are equally risk averse. Some individuals seek out risk in order to confront “limit-experiences” (expérience limite), and never feel so fully as alive as when facing danger, death, and the possibility of personal annihilation. [8]

If we set aside the danger of interstellar travel as an artifact of risk aversion, knowing that risk tolerance is one of those individual variations that drives natural selection, we are left with the argument that interstellar spaceflight would be too expensive and too difficult to pursue. The potential cost of interstellar travel is a matter for another essay on another occasion, but I will only observe here that we do not yet know the economics of supercivilizations, so we must keep an open mind as to whether or not interstellar missions would be prohibitively expensive. I do not think that interstellar travel would be too expensive because a fully automated space-based industrial infrastructure, in possession of the energy and materials that are available beyond planetary surfaces, would find few construction projects to be too expensive, as there would be no economic trade-offs between building starships and producing consumer goods.

The idea that interstellar travel is enormously difficult I do not dispute, though I find it strange that anyone would argue for the, “…ease of information transfer via interstellar communication links,” when these links could not facilitate communication over scales of time relevant to civilization, except for communication with the nearest stars. If there were advanced civilizations located at the nearest stars, with which we might communicate over a time scale of years or even decades, we would already know about these cosmic neighbors. If there are advanced civilizations, then, they must be distant from us, and the greater the distance from us, the more unrealistic it is to imagine that civilizations could communicate on a civilizational scale of time.

I find it astonishing that those coming from the perspective of the SETI paradigm (which assumes limits on interstellar travel, whether hard or relatively soft limits) imagine an advanced civilization having the patience to wait thousands or tens of thousands of years for a message exchange, but being unwilling to send out interstellar missions operating on a similar scale of time. Here we must imagine supercivilizations who do not have the patience to develop advanced transportation technologies, but which do have the patience to wait thousands of years, or tens of thousands of years, or hundreds of thousands of years, to exchange messages with another civilization. For a stagnant supercivilization, this is easily imaginable and possible, but for a civilization in its growth phase, on the path to attaining supercivilization status, a thousand years of technological development is many times longer than terrestrial technological development since the industrial revolution, which has taken us from sailing ship to spaceship.

If a civilization were to send out a message, then collapse some thousands of years later, and the response to the message were then to arrive for some successor civilization still more millennia later, this could be not considered a conversation among civilizations. Under these conditions, only one-way messages make any sense. However, if relativistic spaceflight were to be developed, the intelligent progenitors of a civilization could travel directly to other civilizations and converse with them face-to-face (if both parties to the conversation possessed faces, that is). Now, it is true that civilization on the homeworld of this intelligent progenitor species would experience the same time lapse as beings who stayed on their homeworld and attempted to communicate by conventional SETI means, but those who actually traveled and experienced time dilation could directly experience all that there is to be experienced in the universe. A species in possession of relativistic spaceflight could always arrange for rendezvous with similarly time dilated communities to which they could return. Such a civilization would be “temporally distributed.” This is the argument I attempted to make, however imperfectly, in my previous Centauri Dreams post, Stepping Stones Across the Cosmos, though I suppose I didn’t explain myself adequately.

It beggars belief to suppose that a civilization in possession of relativistic spaceflight would choose to remain on its homeworld, waiting for signals thousands or millions of years old, when it could go out into the cosmos and investigate matters firsthand and to engage with the intelligent progenitors of other civilizations (if there are such) as peers, i.e., as fellow beings. I do not say that it is impossible that this should be the case, but it strikes me as extremely unlikely. If human civilization came into possession of relativistic spaceflight technology, and only one percent of the present human population of (more than) seven billion were interested in this development, there would still be seventy million human beings exploring the universe, and arranging rendezvous with groups having experienced similar time dilation and so belonging to the same historical period (and thus having something in common).

It is not uncommon, however, to view SETI not as predicated upon the impossibility of interstellar flight, and therefore as a substitute for direct contact, but rather as what we can do right now to establish contact, with interstellar travel still in the offing, yet to play its role when our technology achieves that level of development. In this sense, the SETI paradigm and actual exploration are in no sense inherently in conflict. It is entirely possible that a spacefaring civilization might possess a capability to explore relatively nearby planetary systems and yet eventually find itself at a very great distance from any other civilization, with which it could only communicate by electromagnetic means. Both of these enterprises—exploring nearby planetary systems, even if they have no life and no civilization, and communicating with other civilizations too distant for direct travel—would be profoundly stimulating to a civilization in scientific terms. Nevertheless, the SETI paradigm remains a powerful point of reference because in internal coherency of the assumptions it makes.

The advocate of the SETI paradigm must assert that interstellar travel is impossible, because, if it is possible, the idea of a grand Encyclopedia Galactica existing in the form of a network of SETI signals crisscrossing the cosmos is very unlikely to be realized. Thus this cluster of assumptions that I call the SETI paradigm —that interstellar travel is difficult or impossible, that communication is easy, and therefore SETI and METI are, or ought to be, the focus of the efforts of advanced civilizations to interact with peers—hang together by mutual implication. If we reject any one aspect of the paradigm, it falls apart. [9] The SETI enterprise may remain, but it becomes a small part of a big picture, and is no longer the big picture itself.

[Are we confined to our oasis in space?]

Is planetary endemism the eternal truth of humanity?

For some scientists, not directly concerned with SETI as an alternative for exploration, expressing the difficulty of interstellar travel and the unlikelihood of human beings traveling to other worlds has been a way to express the spirit of seriousness (yes, I am invoking Sartre [10]) in relationship to human planetary endemism, since the prior seriousness of our cosmological disposition (our Ptolemaic centrality) was deprived us by the Copernican revolution. No longer at the center of the universe, and schooled in humility by hundreds of years of Copernicanism, we have become acculturated to our apparently marginal role in the universe, and one way to express this idea is to assert that our marginal status is bound to our marginal homeworld orbiting a marginal star in a marginal galaxy.

Given this acculturation, our attachment to our homeworld—rather than being a mere empirical contingency, a truth ready-made by the accident of our origin upon a planetary body—is, as Sartre said, “…an ethics which is ashamed of itself and does not dare speak its name.” Instead of saying (though some do say this), “We ought not to leave Earth,” the SETI paradigm tells us, “We cannot leave Earth.” (The “ought” has been transformed into an “is”; it is brute fact, and no longer subject to volition.) And if we cannot leave Earth, our special relationship to Earth is retained. What Copernicanism has taken from us with one hand, it gives back with the other. We once again have a “special” relationship to Earth, though not the special relationship posited by the Ptolemaic system and its Aristotelian embroiderings.

For example, in my earlier Centauri Dreams post How We Get There Matters I quoted this from Peter Ward and Donald Brownlee:

“The starships of TV, movies, and novels are products of wishful thinking. Interstellar travel will likely never happen, meaning we are stranded in this solar system forever. We are also likely to be permanently stuck on Earth. It is our oasis in space, and the present is our very special place in time. Humans should enjoy and cherish their day in the Sun on a very special planet and not dwell too seriously on thoughts of unicorns, minotaurs, mermaids, or the Starship Enterprise. Our experience on Earth is probably repeated endlessly in the cosmos. Life develops on planets but it is ultimately destroyed by the light of a slowly brightening star. It is a cruel fact of nature that life-giving stars always go bad.” [11]

Eminent entomologist E. O. Wilson [12] went even farther than Ward and Brownlee:

“Another principle that I believe can be justified by scientific evidence so far is that nobody is going to emigrate from this planet, not ever.” [13]

Note that these are assertions without argument, though they invoke scientific evidence without actually arguing from scientific evidence. (I am going to quote more of the latter passage in another post to come, as it perfectly exemplifies a particular perspective on the human condition.)

These extrapolations beyond the SETI paradigm are arguably more damaging than the SETI paradigm itself, because it raises planetary endemism to a metaphysical status, seeking to overturn the essence of the Copernican revolution. The original formulations of the SETI paradigm were made by scientists who had clear and unambiguous reasons for favoring SETI communication over actual exploration, but those who have taken up the SETI paradigm as a way to express their skepticism about a spacefaring future have no such reasons, or, if they have them, they do not state them.

[Ludwig Wittgenstein]

Are we dealing with implicit proscriptions?

It could be that those who argue for hard limits to interstellar travel are incorporating implicit boundaries to the discussion, which, not having been made explicit, have not been part of the argument. This is particularly true in relation to a discussion of supercivilizations, which I will try to show below.

“Someone says to me, ‘Show the children a game.’ I teach them gambling with dice, and the other says, ‘I didn’t mean that sort of game.’ In that case, must he have had the exclusion of the game with dice before his mind when he gave me the order?” [14]

This is how people most often talk at cross-purposes, and so we must make an effort to bring such presuppositions to the surface and make them explicit. What I particularly have in mind in regard to implicit boundaries to the scope of a discussion is the possibility that when someone says, “Interstellar travel is impossible,” what they really mean to say is that, “Interstellar travel is impossible within a given time horizon,” or, “Interstellar travel is impossible based on known science and technology.” This is of interest to me in the present context because the longevity of a supercivilization would presumably exceed the bounds of some ordinarily assumed time horizon, so that while most discussion of civilization would not need to address interstellar travel, it might still be allowed that interstellar travel is possible for supercivilizations, and ought to be discussed in relation to them.

Some of the quotes above seem to clearly rule out implicit qualifications to the assertions being made. For example, the quote from Sebastian von Hoerner explicitly stipulates that, “…space travel, even in the most distant future, will be confined completely to our own planetary system, and a similar conclusion will hold for any other civilization, no matter how advanced it may be.” [emphasis added] This doesn’t seem to leave much room for ambiguity. We need to take von Hoerner at his word, and see what it would mean for a civilization to be incapable of interstellar travel regardless of its age or its technological achievements, regardless of where it finds itself in the universe or in the history of the cosmos.

Without making any implicit boundaries of a discussion explicit, the denial of the possibility of interstellar travel becomes the denial of the possibility of interstellar travel by any civilization (1), at any stage of development (2), at any time in the history of the universe (3), by any means (4), and at any location within the universe (5). This would be a very strong assertion to make, and I can’t imagine that many would agree to it if they fully understood that which they were implicitly asserting. [15]

We could take these five implied conditions in turn and formulate how these implicit qualifications to the denial of the possibility of interstellar travel might be formulated if made explicit:

1. Yes, interstellar travel is impossible for our civilization, but not necessarily for some other kind of civilization, and not necessarily impossible for a supercivilization.

2. Yes, interstellar travel is impossible for our civilizationat its present stage of development, but given a sufficiently long-lived civilization interstellar travel might be possible.

3. Yes, interstellar travel is impossible at the present time in the history of the universe, but it may be possible at some other time when, for instance, another star approaches the sun closely enough for us to travel to it. [16]

4. Yes, interstellar travel is impossible for known technologies, but we may yet develop technologies that will make it possible, or these technologies may be developed by other kinds civilizations.

5. Yes, interstellar travel is impossible for us, located in a diffusely populated arm of our spiral galaxy, but it might be possible for civilizations located in regions of the galaxy where stars are more closely spaced (such as galactic centers, globular clusters, or merely closely-packed regions of elliptical galaxies).

When we put together the possibilities of different kinds of civilizations (including the different kind of civilization our civilization may become in the future), at different stages of development, at different times in the natural history of the universe, involving different means of transportation, and in other parts of the universe when stars are not as diffusely distributed, it seems a bit contrarian (and I don’t mean that in a flattering way) to insist that any and all interstellar travel is impossible.

A further implicit qualification may be present. Disavowals of the possibility of interstellar travel might be interpreted as specifically addressing the known cosmological circumstances for terrestrial civilization only, or such might be more widely interpreted as holding for any civilization that shares Earth’s cosmological circumstances, or, more widely yet, may hold for civilization whatsoever. In the narrowest of these three senses, the implicit qualification may be made explicit by asserting the proviso, “Well, yes, interstellar travel might be possible under these circumstances, addressing the above qualifications as we have done, but since we are likely the only civilization in the galaxy, the particular cosmological circumstances of Earth and terrestrial civilization are the only cosmological circumstances that really count. A civilization located in a globular cluster where stars are less than a light year apart might be able to pursue interstellar travel, but there are no civilizations; this class of civilizations is the empty set, so we may set it aside.”

By this same reasoning, any consideration of what supercivilizations might accomplish can also be set aside, because terrestrial civilization is not a supercivilization, and if we limit ourselves to what terrestrial civilization is now, and what it can do now, where it is located now, and so on, then we can dismiss the possibility of interstellar travel. (We can also dismiss any future for ourselves other than an eternally-iterated present.) Moreover, we have no particular reason to believe that terrestrial civilization will become a supercivilization, even if it survives for thousands of years or more. Whether or not a civilization does or can develop into a supercivilization may be entirely a matter of mere historical contingency, and, in this sense, the particular cosmological circumstances of Earth will mean the difference between whether terrestrial civilization can develop into a supercivilization, or if it will inevitably fail to do so. Moreover, whether or not a supercivilization stagnates or continues to develop may also be entirely a matter of mere historical contingency (an artifact of galactic endemism, as it were).

[“…we have all entered the Interstellar Age.” Jim Bell]

Is interstellar travel inevitable for long-lived civilizations?

When we combine technologies already known to us, despite our rudimentary development as a technological civilization, and the changing circumstances of the galaxies, which will, over a cosmological scale of time, move some stars closer to us (as other stars move farther from us), denying the possibility of eventual interstellar travel is like denying the possibility of what is already known. It is arguable, then, that interstellar travel is inevitable for supercivilizations. If a civilization persists for a period of time sufficient to become a supercivilization, it would persist through additional stages of development, through changing distances among stars, and through changing cosmological conditions, so that a settled and deliberate avoidance of interstellar travel would seem to be a precondition of a very old and advanced civilizations that never achieved interstellar breakout. We cannot rule this out, but we also cannot assume that every civilization will cultivate a settled and deliberate avoidance of space travel.

We are already capable of sending out a spacecraft into interstellar space. The “grand tour” gravitational assist of the Voyager probes has already sent Voyager 1 outside the solar system, though that was not part of the original mission of that spacecraft, and the spacecraft is not on a trajectory specifically tailored to encounter another star (though it may pass near another star over sufficiently long scales of time). But Voyager is in interstellar space, and in virtue of this Jim Bell has asserted, “…now the Voyagers are leaving the protective bubble of our sun and crossing over into the uncharted territory between the stars… we have all entered the Interstellar Age.” [17] By this measure, terrestrial civilization has already achieved interstellar breakout.

The gravitational assist that has been extensively employed to send robotic probes throughout our solar system, if specifically tailored to interstellar purposes, could significantly improve on Voyager’s trajectory in terms of getting a spacecraft to another planetary system. Given the possibility of an interstellar gravitational assist (cf. The Interstellar Gravitational Assist by Paul Gilster), and the possibility of selecting a trajectory specifically for the purpose to traveling to a star brought relatively nearby to us (i.e., optimizing the gravitational assist for an interstellar trajectory), even if terrestrial civilization stagnated at or near its present technological level of development, it would still be capable of interstellar travel if it endures for a sufficient period of time.

Similar considerations hold civilizations that happen to find themselves in cosmological circumstances more amenable to interstellar travel. In their paper “Globular Clusters as Cradles of Life and Advanced Civilizations” (which I discussed in The Globular Cluster Opportunity), R. Di Stefano and A. Ray discuss the possibilities for advanced spacefaring civilizations in globular clusters, where stars are more closely distributed and travel times between stars and their planetary systems would therefore be shorter than travel times among stars as we typically find them distributed in the arms of spiral galaxies. [18]

[“Assembling a Space Station” by Klaus Bürgle]

Would we recognize another stagnant supercivilization as a peer?

Even without “breakthrough” technologies, utilizing the science and technology available to a civilization a couple of hundred years into its industrial revolution, interstellar flight is conceivable, and, under some circumstances, practicable. Unique cosmological circumstances in which relatively low technological interstellar travel is possible may serve as incubators for spacefaring civilizations, which, under this unique selection pressure, would be more likely to develop the sciences and technologies conducive to the expansion of spacefaring civilization, and which would definitely lead to the development of the practical engineering skills necessary to (even nearby) interstellar travel.

Such a civilization would have far more practical engineering experience in spacecraft and living in space than we possess, even if it did not possess any science or technology that we do not also possess. To a certain degree (though not to an absolute degree), engineering expertise can vary independently of scientific knowledge and technological development. (Technologies have often grown out of engineering experience, so that technology and engineering tend to be more tightly-coupled than science and engineering.) We are reminded of this when we consider the lithic technology of Pleistocene human beings, or the stone-working technologies of early civilizations and their monumental architecture, the particular engineering techniques of which have been lost, and which are thus mysterious to us. Analogously, a spacefaring civilization with greater engineering experience in space than contemporary terrestrial civilization, but no greater scientific knowledge, initially might appear mysterious to us.

A truly ambitious civilization of this kind, perhaps not greatly technologically advanced, but with a determination to project itself into the cosmos, could, over cosmological scales of time (if it could survive that long), pass from one planetary system to another as stars passed nearby each other, pursuing a strategy of opportunistic interstellar travel, hopping from one nearly planetary system to the next, as the occasion presented itself. Such a civilization need not be advanced much beyond the level contemplated by Wernher von Braun in his mid-twentieth century plans for a space program that could ultimately, “…build a bridge to the stars, so that when the Sun dies, humanity will not die.” [19] A rudimentary spacefaring civilization of this kind could, over millions of years, expand throughout a significant portion of the galaxy. They might even be so “quiet” in electromagnetic terms, and leave such a light footprint on the galaxy, that we do not see them coming.

It would be a shock for us on Earth if we were eventually “discovered” by some civilization less technologically advanced than we are, but more keen on space exploration, and willing to invest blood and treasure in the effort when terrestrial civilization is not yet willing to invest in the enterprise. For if terrestrial civilization endures to become a supercivilization, but remains tightly-coupled to its homeworld, fearful to extend its reach into the cosmos, we are likely to be “discovered” rather than being the ones to do the discovering. Carl Sagan once wrote, “The surface of the Earth is the shore of the cosmic ocean… Recently, we have waded a little out to sea, enough to dampen our toes or, at most, wet our ankles. The water seems inviting. The ocean calls.” [20] Though the ocean calls, we have hesitated on the shore. Given a sufficiently long period of time—a scale of time over which a supercivilization might endure—there may be other civilizations that do not hesitate.

In my last Centuari Dreams post, Synchrony in Outer Space, I argued that civilizations can retrench from development that becomes so rapid as to be disorienting and socially disruptive, and that this may have happened with the mid-twentieth century space program, which was defunded and neglected after the Apollo Program, but which could have been expanded, had the political will been present (cf. Late-Adopter Spacefaring Civilization: the Preemption that Didn’t Happen). In the event of a (counterfactual) expansion of the mid-twentieth century space program, the history of terrestrial civilization would have bifurcated sharply from the path it did in fact take.

If we encountered a civilization that had taken an earlier path to spacefaring civilization, would we recognize them as the path not taken by terrestrial civilization, as being, in a sense, a peer civilization? This would be the meeting of two different kinds of stagnant supercivilizations—one that stagnated scientifically, but which expanded beyond its homeworld, and another that continued to expand the frontiers of scientific knowledge, but which stagnated on its homeworld—neither of them the kind of supercivilization that runs into the limit of the carrying capacity of the galaxy, and neither of them in possession of relativistic spaceflight technology.

These two civiilzations, supercivilizations in virtue of having endured for cosmologically significant periods of time, might be identified as instances of partially stagnant civilizations, and, in this sense, suboptimal civilizations (more specifically, suboptimal supercivilizations). If we acknowledge the possibility of suboptimal partially stagnant civilizations, we would not be surprised that such civilizations had not exhaustively colonized the entire galaxy, and that they had not built a powerful SETI beacon. Many such civilizations might be simultaneously present in the galaxy and yet know nothing of each other. This could be called the “suboptimal hypothesis” in response to the Fermi paradox.

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Notes

[1] “On the Inevitability and the Possible Structures of Supercivilizations,” Nikolai S. Kardashev, in M. D. Papagiannis (ed.), The Search for Extraterrestrial Life: Recent Developments, Proceedings of the 112th Symposium of the International Astronomical Union Held at Boston University, Boston, Mass., U.S.A., June 18–21, 1984, Springer, 1985, 497-504.

[2] Galactic ecology has been characterized thus: “The timescale for the Galactic ecology is determined by the rate of star formation and the lifetime of the most massive stars (a few million years). This ecology must have existed, though in gradually changing form, over the life of the Galaxy. It is driven by the energy flows from the massive stars, and the material cycle through these same stars. Carbon, and heavier elements, are created in the massive stars, and released through winds and supernova explosions. They cycle between the various phases of the interstellar medium, before again being incorporated into stars and, in some cases, planetary systems and life. Further star formation in a molecular cloud is self-regulated by the massive stars already forming, and by the cooling agents which are already present in it. These agents gradually change as the elemental abundances, particularly of carbon, increase as the Galaxy evolves.” Michael G Burton, “Ecosystems, from life, to the Earth, to the Galaxy” (2001)

[8] Of limit-experiences Michel Foucault wrote, “…the point of life which lies as close as possible to the impossibility of living, which lies at the limit or the extreme.” Foucault, Remarks on Marx, semiotext(e), 1991, p. 31. In relation to John Rawls’ famous thought experiment characterizing a just society as one in which the society is constituted from behind a veil of ignorance as to our place in that society, it has been pointed out that the implied risk aversion is in no sense universal, and there are many who might favor a less “just” society on the premise that an able individual not opposed to risk-taking may make a better place for himself in such a world through his own effort.

[9] In calling this the “SETI paradigm” I do not mean to imply that everyone engaged in SETI accepts this paradigm, nor do I wish to argue against the legitimacy or indeed the importance of SETI, which I view as a worthwhile endeavor.

[10] Of the spirit of seriousness Sartre wrote, “The spirit of seriousness has two characteristics: it considers values as transcendent givens independent of human subjectivity, and it transfers the quality of ‘desirable’ from the ontological structure of things to their simple material constitution. For the spirit of seriousness, for example, bread is desirable because it is necessary to live (a value written in an intelligible heaven) and because bread is nourishing. The result of the serious attitude, which as we know rules the world, is to cause the symbolic values of things to be drunk in by their empirical idiosyncrasy as ink by a blotter; it puts forward the opacity of the desired object and posits it in itself as a desirable irreducible. Thus we are already on the moral plane but concurrently on that of bad faith, for it is an ethics which is ashamed of itself and does not dare speak its name. It has obscured all its goals in order to free itself from anguish. Man pursues being blindly by hiding from himself the free project which is this pursuit.” Sartre, Jean-Paul, Being and Nothingness, New York: Washington Square Press, 1969, p. 796.

[11] Peter Ward and Donald Brownlee, The Life and Death of Planet Earth: How the New Science of Astrobiology Charts the Ultimate Fate of Our World, New York: Henry Holt and Company, 2002, pp. 207-208.

[12] Of Wilson I recently noted, “…the major ideas that have marked his scientific career — island biogeography, sociobiology (which turned out to be evolutionary psychology in its nascent state), biophilia, multi-level selection, of which one component is group selection, and the recognition of eusociality as a distinct form of emergent complexity—are ideas that I have used repeatedly in the exposition of my own thought.” I repeat this here so that the reader understands that I in no sense impugn the scientific work of Wilson.

[13] E. O. Wilson, The Social Conquest of Earth, Part VI, chapter 27.

[14] Wittgenstein, Ludwig, Philosophical Investigations, Macmillan, 1989, between sections 70 and 71. This remark is not included in all editions of the Philosophical Investigations, e.g., it does not appear in the 50th anniversary commemorative edition.

[15] The argument I am employing here closely parallels the argument that G. E. Moore makes against unqualified formulations of utilitarianism in his short book Ethics. It is interesting to note in the present context that Moore’s argument against utilitarian takes as a counterfactual unanticipated by unqualified formulations of utilitarianism the possibility of extraterrestrial beings who would not respond to pleasure and pain as do human beings.

[18] Farther yet in the future, after the Milky Way and Andromeda galaxies have merged, and the stars of these galaxies will have been significantly rearranged, so to speak, our sun will have run its race, but many stars that are relatively isolated in regard to their stellar neighborhood may find themselves suddenly (on a cosmological scale of time) with a close neighbor, and vice versa. In this way, the cosmological context of any given planetary system might be radically altered over time.

Communication through quantum entanglement (which is what I understand by Le Guin’s “ansible”) as we understand it at the present time is limited to communication between originally entangled particles that have later been separated. So you still need actual physical space flight to separate them to cosmological distances. Now, there is physics we don’t know yet, and this may change the possibilities for communication. However, this would involve science and technology beyond the level of contemporary terrestrial civilization, and beyond our immediate ability to forecast near-term developments in science and technology. Given this qualification, it does not address my example of a civilization that stagnates scientifically but expands cosmologically.

Le Guin’s “ansible” must use something else than quantum entanglement. FTL communication is not a consequence of entanglement.
See No-communication theorem in Wikipedia.
Also
Lectures on Quantum Mechanics 2nd Edition, Steven Weinberg. 2015.

Right, took me a long, long time to understand that, because all the popularized accounts of the experiments, aimed at laymen, are simplified in exactly such a way as to conceal this. They always omit the little details that make this clear.

I’ve come to really loathe popularized accounts of science, for just that reason.

One trait that appears to be universal to all of the advocates to “staying home” on Earth, such as E.O. Wilson and Kim Stanley Robinson, is an implacable hostility towards pioneering of the Jackson/Heinlein context. I believe this motivation serves as the basis of their opinions on this matter.

It would be worthwhile to analyze the ideologies involved in “staying home” vs. cosmic expansion, which would be an analysis of nascent ideologies not yet fully formed. If a civilization launches itself upon exploratory journeys in the cosmos, these experiences are likely to profoundly affect the moral and intellectual development of intelligent progenitor species involved in the exploration and expansion, so that the ideologies that inspired these efforts would be changed by their implementation.

It is difficult for me personally to understand the hostility that you mention, though I have encountered it, so I know it’s a common view and I would like to be able to understand it. It is not clear to me if this is a temperamental expression of individual variability (and therefore ultimately biological in origin, which in this instance means an expression of our evolutionary psychology) or if it is more cultural and due to particular features of education, acculturation, and the peculiarities of the present stage of the development of our civilization. Nature vs. nurture. I guess it’s probably both.

As an American, I can only talk about the situation in the U.S. There are two major political factions, the liberal-left and the alt-right, that are “illiberal” in the John Locke classical liberal sense. Of the two, the liberal-left is entirely inimical to pioneering and autonomy by self-interested groups. This view is summed up in the recent Kim Stanley Robinson novels. The alt-right, on the other hand, is not necessarily hostile to pioneering per se. But much of their writings is couched in a semi-feudal terms in a manner that they seem to glorify the medieval period in Europe, which was certainly not about pioneering at all. More specifically, they express hostility towards Lockean classical liberalism, which I consider to be the philosophical root of pioneering in the Jackson/Heinleinien context.

I have visited various European countries on business. But I lived in various East Asian countries for 10 years. I can tell you that nearly every European I met does not have a pioneering bone in their body. Its as though they are culturally and even genetically hostile to pioneering in any form.

The East Asian people, particularly the Chinese, are the consummate traders of the world (e.g. Overseas Chinese of SE Asia). The Japanese and Koreans much less so. However, these people as well do not have a pioneering bone in their bodies either (as my Japanese wife will freely admit).

Pioneering appears to be an Anglo-American thing, if not exclusively American.

Given that Europeans of most countries established the USA, I find it hard to believe that there is not a fraction of Europeans that wouldn’t pioneer if given the right opportunity. Currently, there is nowhere on Earth that can be “pioneered” or “settled” that has any value and that isn’t already under some government’s control.

Heinlein’s protagonists were settling worlds that were basically New Earths and suitable for farming. We have no knowledge of any such worlds. As our knowledge of biospheres and ecosystems has vastly expanded since Heinlein was writing his stories, we are less optimistic that such worlds would be suitable for human settlement or even that they should be.

Humans exploiting any world or moon are more likely to be like Asimov’s “spacers”, relying on robots to do the heavy lifting, not like Asimov’s “Earthers” or Heinlein’s gritty individualists recapitulating the colonizing of the N. American continent.

Exploiting and even settling another world is going to look a lot more like the exploitation of offshore oil, a project that requires huge capital resources and expertise that is aggregated into groups. Realistically, enough people and expertise is going to be needed to bootstrap an industrial economy.

There has in the last 4 or 5 decades been a repressive cultural attitude in the UK linking pioneering with colonialism, but there remains a strong streak of bloody minded individualism which given an area of outlet would gladly seize the opportunity to express its self and set off for horizons unknown.

I’m a bit dubious about limiting the pioneering spirit to Anglo-Americans. In the not too distant past, Russians pushed eastward into Siberia and southernly into the Caucusus region — Tolstoy wrote stories about such. In the 16th century Spaniards and Portuguese mariners split the world between themselves, and then were pushed aside by the French and the Dutch (and the English). A few centuries before that, Germany pioneers pushed through what became Prussia and Poland. And before that there were Vikings.

There’s an element in most societies, it strikes me, that would explore and loot or maybe even explore and settle, given proper circumstances. Perhaps we lack such circumstances. Other hand, it might be that the “proper circumstances” include poverty and desperation — something hinted occasionally in those Heinlein novels — in which case that modern humans seem to lack the essential spirit for pioneering might not be something to lament.

A particular concern of mine, and one of the reasons I advocate for a short term push to build von Neumann machines, (Which we should be capable of within just a couple decades if we try.) is the possibility that our push into space will be gradual, resulting in our population growing in proportion to our resources, and no faster.

Fast interstellar travel requires the expenditure of huge resources per mission, and if manned, even vaster per passenger. It isn’t going to happen unless our infrastructure grows enormously faster than our population.

Can’t you see that future: We expand into space, using chemical and solar powered rockets, and human dependent production, our population growing as we expand, until in the far distant future the Solar system is fully populated, without the excess resources to devote to a task as extravagant as interstellar exploration, because our needs have grown in synch with our capacities? The huge resources of the Solar system matched by a huge population.

In that scenario we probably still expand into the galaxy, comets and Kupier belt objects will eventually be colonized, and we’ll cross the interstellar depths by slow diffusion, as our own thinning constellation of objects blends imperceptively into the next stars’ cometary belt.

That’s not stagnation, as such, because we’d be spreading at the borders, but it’s not a glorious future of relativistic travel and a galaxy claimed by human kind in under a million years.

It’s a good point to note that a civilization slowly diffusing through its own planetary system could grow outward into the Kuiper belt and the Oort Cloud, and my the time there is a presence in the Oort cloud you’re almost half way to the next star. Sure conditions get more difficult the further out you go — less sunlight and fewer resources — but by the time this is possible the expanding civilization ought to have a great deal of experience in these matters.

I think it’s important to note that we do not yet know the economics of interstellar expansion. You suggest that fast interstellar voyages may be too expensive to sustain for a civilization focusing its resources on the maintenance of a vastly expanded population, but I think in the long term, if the technologies of fast interstellar travel prove to be practicable (this is something we also do not yet know), then this will be less expensive than the equally grand vision of a system-wide civilization building vast arks — generational starships — and sending them out into the cosmos.

As Darwin said, “There is grandeur in this view of life,” by which I mean the dispersion of life throughout the cosmos, whether by rapid relativistic means, in less than a million years, or by much slower means, which will come to maturity only over a billion years or more. The ultimate practicability of the various technologies we can now envision will be the deciding factor of the order of temporal magnitude of the dispersion of terrestrial life into the universe.

Regarding the term “stagnation”. Stagnation can mean different things. Discussed was ecological maximization. That limit can only be reached when the resources of the universe are fully and most completely used to green it. In our neck of the woods, that means creating a huge number of space habitats by dismantling the planets. The population size of such a civilization is many orders of magnitude larger than ours.

Economic growth is likely to stagnate too. Our recent historic rate of ~3% pa is not sustainable for very long. Exponential growth soon exceeds that of a Sol system. and surprisingly quite quickly reaches the limits of the galaxy. (< 1 millennium to expand 400 billion fold from a Sol sized economy.)

What isn't likely to stagnate is the sheer number of possible states that civilizations could attempt to create. Just recreating one small historical culture and replaying it so that chance changes outcomes would generate a vast number of new versions. That game has the capacity to rapidly exhaust all of space and time.

So as long as civilizations are not totally static, they should be able to evolve and create new information indefinitely, even if it means restarting from a defined historical and knowledge base periodically.

This is how I interpret the word stagant too.
It would not be a golden age civilization in complete lifelong vacation.
Perhaps part of the population might choose that, or to live in fantasy worlds created in habitats or computer generated illusion.

Earth today is already getting very close to the limit. Not because of technical limitation but because governments and industry choose to make products that drain limited resources and create harmful waste products.

Even if a super civilisation colonise all worlds and moons, or covert all matter completely in big engineering, there would still be economic activity.
And that activity could very well be in ecologic cycles, even if it might be from the collectors of whoopee cushions. ;)

Quote by J. Nielsen: “one that stagnated scientifically, but which expanded beyond its homeworld, and another that continued to expand the frontiers of scientific knowledge, but which stagnated on its homeworld—” This is impossible or science fiction. There is no such civilization that could have any kind of interstellar travel without scientific knowledge. There is no industry without physics or science.

Any civilization that started interstellar travel before us must be much more advanced than us. They evolved before us; Their star system most likely was born before ours or there home planet’s giant impact occurred before ours which would result in a faster evolution.

Based on today’s technological progress which is very slow, practical interstellar travel for people is two million years. This is a conservative view which does not include superluminal technology which might result in an earlier interstellar capability. We could have a breakthrough with FTL technology which would result in an earlier time but that time would still be long like a million years. The reason being is that it takes enormous energy.

There are world ships, but those are still ahead of our technology today. World ships suffer from the idea that they take too long to get too their destination or are too expensive and dangerous since we can send robot or automated craft or probes in the place or we might build a faster technology which would make them obsolete.

Depending on the civilization, interstellar travel could be easy. Very easy. There would be a single massive wave of colonization when the parent civilization builds a hundred billion ships and sends them out. Even at a mere 1/1000th of the speed of light it would only take 100 million years to fully colonize the galaxy. Of course they would be self-repairing robotic ships, but they would be able to recreated the builders once they arrive.

Perhaps that explains the Fermi paradox. 400 million years ago someone did just that and colonized all the rocky planets with high levels of oxygen in their atmosphere. The Earth, not having a high level of oxygen, didn’t get colonized. Then the civilization stagnated, or evolved, or is planning a second wave every 1 billion years to grab planets like the earth. Sure the idea has problems, but so does every Fermi paradox solution.

Even with our current technology we could, with enough time and motivation, build an Orion style interstellar vessel. Whether or not the crew could build a new civilization upon arrival is in question though.

SETI, in my opinion, is not about saying we shouldn’t become an interstellar species, but about looking where we’re going rather than taking a blind leap and trusting only in faith that we can hope to know where we will land. People don’t put on a blindfold when they get into a car to drive – they used both eyes to watch where they’re going. Those that don’t might avoid the inevitable for a while, but will eventually end up in an accident. Few people/civilizations will suvive playing a thousand rounds of Russian Roulette.

Laws of nature aren’t absolute in the sense that elements after Pu-239 can be produced artificially but they almost never appear naturally. Of course there is no way in hell for some random exotica with 1M proton + 1M neutron to exist naturally or artificially; the real limits are based in mathematical consistencies but when one stays too far from the physical boundaries, this becomes SF delusions.

I too am very skeptical that interstellar travel won’t happen in some form. There are just too many options from low tech to high tech and different acceptable time frames.

I personally suspect that our post-human travelers will be synthetic, the “robot” option [IIRC] from a previous post by Nielsen. Like spaceprobes that can have their software changed by remote upload, such synthetics might well offer a way for minds to travel between the stars, whether by em signals or by physical media. Careful timing would allow groups to experience communication with different civs and yet still regroup at the same time and place in the future.

Communication can be “blurred” in meaning if a civ sends a data dump of its state with an AI that could converse with the target civ. While it doesn’t meet the criterion of a civ-to-civ conversation, perhaps we need to think less about such homeworld to homeworld conversations and just accept that travelers meeting still constitutes useful exchange that might eventually affect the descendants of the participating civs. Historically, had none of Columbus’ crew ever returned home, would the communication between his crew and the American natives not have constituted a communication even though Spain did not get to participate?

As in my previous comment, I think this allows any encompassing super-civ to endlessly explore new patterns that will continue to find new ones until the end of the universe.

A good post…
By 2035 the High definition Space Telescope with its 40 foot mirror orbiting the sun should keep your curiosity percolating…There are too many unknowns concerning super-civilizations…Somebody here said only yesterday that we are a sample of one…stay patient…be prepared for surprises…new knowledge changes so many suppositions…Look where America was in 1835…Lucky America changes…Ancient Rome didn’t change…they went back to the land and abandoned Rome…Now Rome has regenerated despite all the tough centuries…You’ve read Asimov and the Foundation and Hari Seldon…regeneration is one of nature’s favorite paths…regardless of who says what…

I am old enough to remember the late 1940’s-early 1950’s uproar over “breaking the Sound Barrier”. All sorts of high-IQ’s were sure it couldn’t be done, and if attempted the result would be fatal for pilot and plane…this even though quite a number of WW2 pilots claimed they had already done so, with no ill effects other than “compressibility”. And then what’s-his-name and the X-1 did it under measured conditions, and that was that. Exactly the same will prove true for the Light Barrier, IF ours or some other galactic civilization lasts long enough. And therein lies the problem. As I explained before,

1) intelligent civilizations involving creatures w/o hard-wired inhibitors against massacring their own kind – e.g., us – enter the nuclear funnel and generally don’t come out. Actually, we’ve caught one enormous break in this respect – see if you can figure out what it is – and so just may navigate through, though I doubt it.

2) those with hard-wired inhibitions against intra-specific massacre can last much longer – even long enough to attain both FTL travel and communication – but sooner or later encounter another suchlike and destroy one another in a Sector War. So at any given time there’s no more than a half-dozen or so of both civilizational types spread randomly across and through the c. 100,000,000 cubic light years of our galaxy. Thus the Great Silence. One thing for sure, E.O. Wilson et. al. notwithstanding: if somehow we murderous, strip-mining humans do get through the nuclear (and other) funnels, the Milky Way Galaxy is eventually going to become a noisy place indeed.

The question at that time, as I understand it, wasn’t whether the “sound barrier” could be broken, (Clearly it could, bullets did it all the time!) but whether people could survive doing it.

And, honestly, there really wasn’t any technical reason to suppose it was impossible to survive, unless maybe you were in an open cockpit plane at the time.

I think these claims were more on a par with the Smalley attacks on the feasibility of nanotechnology. Sometimes a group of “experts” have non-scientific reasons for wanting to declare something impossible, and confuse those motives with scientific reasoning.

Faster than light travel is rather different, we actually do have all sorts of reasons to believe it impossible, and precisely no examples of anything that travels FTL.

galaxies beyond the visible “edge” of our universe are accelerating away from us at greater than lightspeed. That’s why we can’t see them. They do so by stretching/warping spacetime. I expect that, by controlling dark energy, we can eventually do so as well.

800 years ago, the idea that the planets and sun rotated around the earth was actually good science. Geocentric models adequately explained the rotation of the planets until advent of telescopes. The copernican model did not make predictions any better than the geocentric model. The time from copernicus manuscript to gaileo was 100 years. When heliocentrism became dominant, not only did the view of the solar system change so did the view of the universe since heliocentrism required stars to be much more distant. If FTL travel is possible then the science needs to catch up with the theories.

Honestly, comparing the sound barrier with the light barrier is a very bad analogy. They are entirely different things.

And then what’s-his-name and the X-1 did it under measured conditions, and that was that. Exactly the same will prove true for the Light Barrier, IF ours or some other galactic civilization lasts long enough. And therein lies the problem.

First off, there was no question whether the so-called “sound barrier” could be broken. Bullets and whips have been breaking the sound barrier for centuries (indeed, the sound of a whip crack is a small sonic boom). The question was purely whether an aircraft could break the sound barrier in controlled flight. Earlier aviators found things to behave quite differently in the transonic regime once their aircraft hit those speeds, and tended to lose control.

But we know of nothing that travels faster than light, locally. And relativity, which is supported by a rather convincing amount of evidence, suggests that nothing that carries energy or information can outrace light. Worse, if we assume something can anyway, in relativity you can construct scenarios in which FTL trips result in time travel and causality violations.

All that the statement “they said we’d never break the sound barrier, but we did, so the light barrier will be the same” expresses is a blind faith that every predicted natural limit to our activities will be overcome by human ingenuity and technology. It’s equivalent to stating that there are no natural limits on our activities, and this is simply not true. Just look at the history of perpetual motion.

galaxies beyond the visible “edge” of our universe are accelerating away from us at greater than lightspeed. That’s why we can’t see them. They do so by stretching/warping spacetime. I expect that, by controlling dark energy, we can eventually do so as well.

That aside, you are referring to the Alcubierre Metric. The idea that a spacecraft might achieve apparent FTL but riding a wave of expanding and contracting spacetime is intriguing, but unfortunately it’s still an entirely mathematical construct that may not be physically meaningful. Galaxies do not travel faster than light by warping spacetime. They, like us, are embedded in the expanding spacetime of the universe. Alcubierre Drive requires controlling or “engineering” spacetime, an entirely different matter.

And you need negative mass (typically an astronomical quantity of it) to create this metric, not dark energy. Assuming we can figure that out, we then have the issue of controlling the bubble (which is disconnected from the ship inside it), being fried by Hawking Radiation at superluminal speeds, and accidentally destroying the destination once you arrive. And you still have the possibility of causality violations. The concept definitely deserves attention, but don’t count on it leading to warp drive. If a physics breakthrough is uncovered (read, if the universe turns out to work the way we’d like it too), just maybe it might. But it could just as easily be impossible to construct.

Humanity is a primitive race, driven by reproductive urges and engaging in murderous wars. Our home world is threatened by destructive cosmic events. Our environment is our own cesspool. As a species considered as a whole, our objectives are sex, food, entertainment, and comfort. We seem more likely to obtain our needs by taking from others rather than to produce our own. Our view of the universe seems to be an extrapolation of our current experience. I do not know if it is possible for any human to imagine what a successful long term civilization would be. I do not that we would want it if we could so imagine. A hive society come to my mind . . .

Our society has stagnated for over a hundred years when you look at the average person use of power, the HORSEpower of the sacred automobile! When society excepts EmDrives, LENR (Cold Fusion) and the ability to transmute elements, then and only then will we become a planetary society that can really contemplate the possiability of intersteller travel in a knowledgeable way. The wisdom embedded in the quantum universe will lead us to understand and fathom the electromagnetic properties of the photon and its relation to the electrons phase locked cavities, the base root of all energy and the key to interstellar travel.

Wonderful article.
And surprisingly, this has to be repeated and to justify again and again.

The idea of the possibility of interstellar travel in the star approaches described well-known geologist and paleontologist Ivan Efremov in his book “Star ships” (https://en.wikipedia.org/wiki/Stellar_Ships). Now the story about the aliens among dinosaurs looks corny, but the book was written before the end of the Second World war.

In addition, the movement of the stars can be controlled in the presence of very limited resources, and these technologies are also already known (Shkadov, L. M. “Possibility of controlling solar system motion in the galaxy, «38th Congress of the …», October 10-17, 1987, Brighton, UK, paper IAA-87-613.).

This completely changes the paradigm of interstellar flight as a contradiction with the life on the inhabited planets (by Edward Wilson, etc.), as the contradiction is removed.

Thanks. I should have mentioned the Shkadov thruster in this post, as it operates over the time scales I examine in this essay, and it would speed up the process of bringing other planetary systems within easy spacefaring range of a civilization without exotic drive technologies. The idea of a Shkadov thruster is pretty basic, the question, then, would be whether building a Shkadov thruster around one’s own star would take engineering expertise beyond what could be expected from a rudimentary spacefaring civilization. Obviously, we could define a number of stages of spacefaring sophistication and differentiate those capable to carrying this off, and those not so capable. The distance scales of the universe would then become a strong selective effect: those civilizations capable of mastering the engineering of a Shkadov thruster would have “first mover” advantage in settling the galaxy and displacing any lower technology rivals, or leaving nothing available (no unoccupied real estate) for Johnny-come-lately spacefaring civilizations.

Perhaps as inportant as anything else are societal, cultural, political, moral and ethical considerations. Less than altruistic motivations and actions, fouling our own cosmic nest, lack of perspective in managing non-renewable resources can each severally and jointly do us in, and might well be likely to do so.

As we do not yet possess a quantifiable model of civilization (unless you count Turchin’s cliodynamics), we don’t have any numbers associated with components on the graph. If some tech billionaire would like to drop in endowment in my lap, I would gladly set up a research institution devoted to the study of civilization, and which might eventually start filling in the numbers for the graph above.

In my uncertified intellectual opinion…
Interstellar travel is not a heck of a lot more likely than FTL travel.
The former requires the latter.
This must not be easy to do; if it was, then the Fermi busters of the galaxy would be buzzing around regularly.
Einstein did NOT have the whole picture (neither did Newton, neither did Bohr). But every one of Albert’s predictions based on his incomplete theory have proven correct (compare Albert’s list to those of String Theory). Now add gravity waves to the list.
I don’t think FTL is normal, quantum gravity space is possible, else everyone out there would be doing it. Or if no one is out there.
Unless a way can be found to do an end run around relativity, to cheat Einsten, then we’re stuck in the solar system.
Yes, slower than light can be done, and it SHOULD be done. But to get to supercivilization status that way would take a very long time indeed. Without the FTL, humans cannot get there. Robots, the future belongs to you.
Why did the galaxy have to be so big?? I know, for no reason.

Let’s just keep trying to explore and get out there any way we can. Our species will always have a finite biological lifespan but with future technology likely to increase that we have an incredible opportunity to explore if we don’t destroy ourselves. At the very least we will be able to send machines to nearby starts very soon. I’m very skeptical about super civilizations but possibly only because I lack enough imagination. There are many negative feedback loops as well as positive ones that may prevent a super civilization from dominating even one galaxy.

We still have many possibilities for the buildout of spacefaring civilization, and we still have many possibilities for failure. Suboptimality occupies a position somewhere between a glorious onward and upward future on the one hand, and, on the other hand, ignominious failure.

First, as a formerly expanding civilization reaches the limits of resources there may be a tendency to overshoot, due to the inertia of a civilization reforming itself from the values of an expanding “frontier” (in figurative terms of development if not literally in terms of colonization) culture to a steady-state culture. Thus a civilization might temporarily over-utilize finite resources, then suffer a crash due to their depletion, before finally reaching an equilibrium. The curve showing the civilization’s approach to K the carrying capacity might have a squiggle or two of over/undershoot before leveling out at K.

Second, the maximum utilization of resources possible given the laws of physics may not be realized in one go. A civilization might reach the limits of the technology available to it, fall into a near-steady state for a period, and only then make a technological breakthrough which wasn’t possible until a sufficient economy of scale was reached. To imagine one hypothetical, it might be possible to develop a technology based on manipulating gravity but only after engineering on a literally astronomical scale becomes practical: creating artificial neutron stars from stellar-mass quantities of iron for example. So the approach to the absolute limits to what’s physically achievable may characterized by a number of temporary plateaus rather than a single development curve.

I thought about using a graph showing overshoot (there are many of these available that I could have adapted), but I chose the flat line K for the sake of simplicity, but you’re absolutely right that one would expect to see an overshoot and then an oscillation around the K mark.

Also, I agree that it is likely that spacefaring buildout will occur in a two-steps-forward-one-step-back fashion rather than a linear (or, rather, sigmoid) convergence upon K. In a more sophisticated formulation of the suboptimal hypothesis to come (fate willing), I will argue that convergence upon K, far from being inevitable, would be very rare, even if there are mulitple spacefaring civilizations developing under conditions conducive to their continued growth. Too many things can happen over a million year time span that would derail a steady sigmoid growth curve to carrying capacity. On Earth, on much smaller scales of space and time, organisms routinely converge on K, but at the scale of supercivilizations I think this will be exceedingly unlikely and therefore rare.

In any case, you’ve written a very nice summary in two paragraphs, and this sort of approach could be fruitfully developed as a way to study spacefaring civilizations, eventually providing some numbers to a quantifiable formalism, as I suggested in my response to the questions posed by Al Jackson (above).

One of the ideas in the book Frontiers of Propulsion science is a gravitational wave rocket. As we explore the depths of matter at an even smaller scale with higher energies we will discover the graviton. If not in the LHC, it will occur in a larger, more powerful collider. It is just a matter of time before we can make the technology to manipulate the force of gravity. I doubt we will ever have to wait long enough to make supernovas and neutron stars to achieve that.

The possibilities for the physics we don’t yet know are fascinating, and if new physics produces novel technologies for us to travel through the cosmos, then all the better. But what if the scientific stagnation of our civilization becomes so entrenched that we never build a collider more powerful than the LHC (and its eventual updates)? Suppose scientific knowledge (in physics) stagnates at the level that can be provided by research run on the LHC and its upgrades. We may never get to the point when we can put quantum theory and general relativity together, and the technology to control gravity would remain beyond our ability.

In this case, if we were to travel through the universe, we would have to choose between methods known to us on the basis of contemporary physics (slow travel such as I described above, generational starships, relativistic travel, and so on). One of the things that I have tried to show here is that this latter option isn’t really all that bad. It would take a long time for such a civilization to occupy its own galaxy, but it could be done over hundreds of millions of years if a civilization could endure for that long.

Of note about traveling the universe.
Distance = speed X time
What if the travelers master time rather than speed?
I mean mastering biological time by techno-bio-physics-electro-cyber-robo-augmented-…you-name-it. Sophonts that live 10,000, 100,000 , a million , more, years.
One could noodle along at .1% , .01% the speed of light and travel a great amount of real estate in the universe.
Such civilizations would have philosophies and modes of operation as to be , well, indistinguishable , not from magic, just indistinguishable !
This could well be an answer to the Fermi Question.

Charlie Stross’ “Neptune’s Brood” does exactly that. The robot protagonists basically slow down their time perception to make sub-light star travel feasible. The idea was earlier suggested in his earlter “Saturn’s Children” for interplanetary flight. Isn’t Schroeder’s “Lockstep” a similar concept using hibernation, an old SF idea?

Athanasia-istic aliens are standard constructs in prose science fiction , going back a long way. Though they are not entirely common.
As expected Arthur C. Clarke is best known for this kind of concept. The best example being the Monolith Makers in 2001 A Space Odyssey.
As always science fiction on the page proves a story-for-that , more than any other source.

Ultimately, technological advancement is restricted by physics and quantum mechanics. Until those limits are reached….
One explanation for ‘stagnation’ would be immortality of individuals and collectively, the entirety of a civilization by way of migration from organic to non-organic quantum minds. Communication/sharing via quantum entanglement allows a civilization to appear stagnant to organic life, as the ‘quantum civilization’ would not experience ‘time’ as the organic one would. Migration to ‘quantum state’ would drastically alter resource consumption, reducing consumption to maintenance requirements. Interstellar activity would be done for a much different reason – the dispatch of probes with ‘instantaneous quantum entanglement’ capability, for the purpose of instatanously expanding the ‘virtual experience’ and knowledge of the civilization. Bottom line, stagnant super civilizations would not engage in interstellar travel, however, they continually ‘expand’ and experience the universe at all ‘levels’ of existence.

It’s worth reading if you’re not familiar with this line of argument. Smart and those associated with him (like Cadell Last, whom I heard speak at the second IBHA conference) are highly critical of the “expansion hypothesis,” so this is very different from my own approach, which is much closer to the expansion hypothesis. I’ve been meaning to write a Centauri Dreams post focusing specifically on the expansion hypothesis and its critics, but I haven’t made the time for that yet.

When I was writing the above I actually had a modified version of Smart’s transcension hypothesis in the back of my mind as the foil to the slowly expanding (relatively) low technology spacefaring civilization. A suboptimal transcension would still leave a civilization tightly-coupled to its homeworld with a somewhat robust relationships with the outside world, i.e., this would not yet be a civilization entirely turned inward on itself, living exclusively in virtual worlds. The vulgar version of this would be sitting on the couch, eating potato chips, and playing immersive video games until the end of time. Smart’s version is a little more sophisticated than this (needless to say).

PG referenced ‘The City and the Stars’ in the introduction to the main essay. It strikes me that though the civilisation described in Clarke’s book appears pretty stagnant at the outset, the deeper truth discovered in the book is that some of the designers of the civilisation (and it certainly *is* designed) deliberately created a mechanism whereby the society can free itself from the bounds imposed on it. It can release itself from the designed-in stasis at recurring intervals if the conditions for doing so are right. The apparently ‘stagnant’ society might really then be conceived as an engineering solution for achieving a very long term civilisational goal. Without going into the thinking and purposes of the designers in the novel, I think we can take the more general point that stasis and civilisational stagnancy might actually be used as a tool – a means to an end and with an inbuilt ‘de-stagnate’ contingency mechanism. Further that civilisation itself might actually be something that could be engineered.

Given the bloodbath that was the twentieth century, I suspect thinking along these lines gives a lot of people the creeping horrors. Nevertheless, it doesn’t break the laws of physics, and some other civilisations might find it easier to tackle than perhaps ourselves.

Also on the subject of not needing to break the laws of physics, consider that we could send earth creatures to another star and have them live out their lives there right now. Tardigrades, once dehydrated, turn into little blobs called ‘tuns’. A tun can be cooled down to absolute zero. Once warmed back up again and rehydrated, the tardigrade will come back to life and start wandering around doing its thing. At absolute zero, all chemical processes halt, entropy ceases to increase and time itself essentially stops. A tardigrade tun at absolute zero in a radiation hardened box could make the trip to another star even at a voyager-level snailpace. As long as the machinery for warming it up again at the far end worked without problem we would have successfully sent living animals to another star system.

By simple extension, if we could figure out a way to cool a human being down to absolute zero, leave them there for the span of a tea break, and then reheat and revive them again, then this in itself would solve the “interstellar travel” puzzle. Fifteen minutes at absolute zero is the same as fifteen thousand years, given strong radiation protection. We don’t need to do any clever new physics to transport people to other stars, just clever biology. And lets not forget that this would also enable time travel into the future without any physical travel through space itself, providing us some other capabilities and options, such as have been discussed on CD elsewhere.

Think about the wealth and power created by super-automated, hands-off manufacturing by self-replicating hardware (something that I think really needs a naming), the energy resources of a star and the material resources of a planetary system. Now think about the power for direct exploration of space afforded by cryogenics (should this be achievable) coupled with the limited space transport technology we already understand how to create. These things together provide *opportunities* to extend a civilisation’s reach both physically outwards and temporally onwards. The component missing with trying to suss out whether long term stagnation is on the cards is purpose. One might consider our present planetary civilisation’s purpose, such as it has one, as the meeting of the material needs of its inhabitants. Before this century is out, if we can avoid destroying ourselves, we will be in a position to meet those needs with minimal time, effort or attention from ourselves. The questions of what purpose we will then create for ourselves are already starting to make themselves felt. Thinkers such as Nick Bostrom are looking into existential risks. We could use some more attention paid to the existential opportunities!

Marshall McLuhan said that the media is the the message; perhaps it could turn out to be greater and maybe actually defining of our civilisation going forward. We have moved so quickly along the curve of new media forms and accelerated networking and social problem solving capability in the last twenty years that we are far, far from any sort of equilibrium or even understanding of what the limits are here. In a world knit far more tightly together perhaps we will converge on a means of articulating and actualising common purposes that we have not yet imagined. A true civilisational ‘discussion’ of long term and large scale purpose could take place and become ongoing using means for defining and rationally considering the arguments yet to be developed. No such discussion could miss the issue of stagnation, or indeed the possible uses of engineered or temporary stagnant periods.

1. Once the tardigrades are thawed out, what are they going to eat? Their continued existence depends on a compatible biology at the target star. It may even require a hospitable ecosystem all teh way down to the microbes and viruses.

2. We cannot freeze humans down to nearly 0K. Unlike animals than that tolerate desiccation, our cells just freeze and burst. The result is the same as freezing and thawing bananas. You get mush. Now that may be solvable in the future as we are able to freeze small organs of experimental animals, so there may be hope eventually. However, since we are now closer to having artificial wombs, it may be easier to revert to sending frozen embryos, which we can do now, and find ways to bring up that first generation. But again, we have the alien biosphere to deal with unless we build habitats with local resources and keep the human descendants inside.

3. The obvious technology to send intelligence to the stars already exists. They are called robots. They can easily stay in stasis for the long journey and “boot up” on arrival. They can operate on almost any world, living or dead. The “only” outstanding issue is how intelligent can they be? That we don’t know, although I would bet that AGI to human level is achievable, even if that intelligence looks very different to human I.

4. If humans do travel to the stars, I would expect robots to go well in advance to terraform worlds ready for human arrival. Their expansionary wave into teh galaxy will be perhaps 1 – 10 millennia ahead of humans.

(1/2). Being tardigrades, they’d probably eat each other! Likely none of the cells of their regular foods have the same sort of disordered proteins or vitrifying sugars or whatever to survive being frozen down without ice crystals mushifying them from within. If you put in some leaves in their little heater box then maybe they’d be happy with a leaf smoothy at the far end?

I should have made myself a bit clearer here. The thought I had in mind writing that was not landing pioneering tardinauts to colonize a remote world; it was to point out that at least _part_ of the problem of biological space travel (getting some sort of complex organisms to a destination remote in space, alive) is solvable already for this special case, without needing to go down the speculative physics route.

Humans cannot at present be frozen down, as you say, but if it is possible to do this to one sort of (just about!) macroscopic living thing, then perhaps we could coax ourselves into replicating the trick. Preventing water molecules from forming ordered ice crystals during freezing so that the cytoplasm cools into a disordered glass would constitute a big piece of the puzzle of cryogenic suspension. There are other pieces as well of course, but at least we have the example of tardigrades to show that we are not necessarily chasing the impossible. IIRC there are also some types of frogs that can survive being frozen solid, and they are much bigger than tardigrades!

I think the alien biosphere issue you mention could actually be a showstopper for settling living worlds for reasons both technical and ethical. Maybe what we really need is a dead ball with an atmosphere within the tolerances of our most invincible extremophile bugs. Bringing our own bottle of bacteria to create the party atmosphere!

We could use civilisational stasis to implement panspermia in a way directly useful to us or our descendants in the way you suggest in (4). We send out our self-replicating robot legions to terraform every dead world they possibly can. They use biota that starts off with a Terran genome, while we around Sol deliberately go into some sort of civilisational suspended animation / designed stagnation. Once sufficient time has passed for the biology to take hold in close systems, the civilisational holding pattern is lifted and off we go to colonise the biologically pre-prepared galaxy!

“I find it astonishing that those coming from the perspective of the SETI paradigm (which assumes limits on interstellar travel, whether hard or relatively soft limits) imagine an advanced civilization having the patience to wait thousands or tens of thousands of years for a message exchange, but being unwilling to send out interstellar missions operating on a similar scale of time. Here we must imagine supercivilizations who do not have the patience to develop advanced transportation technologies, but which do have the patience to wait thousands of years, or tens of thousands of years, or hundreds of thousands of years, to exchange messages with another civilization.”

Precisely. I understand why SETI have advocated transmitting over travelling: It is a combination of not wanting to be lumped in with the UFO crowd and the long-standing view that interstellar travel is very difficult – which it is, but not as impossible as once seemed. Paradigms will continue to change as we get smarter.

I saw some of this bias in action in 2000, not so long ago. I was at a SETI conference at Harvard. The very first slide (on an overhead projector, no less) was a roughly hand drawn image of an overly complicated starship concept, an antimatter one at that. The panel of presenters used it to show just how tough, even absurd it was, to imagine even an advanced technological civilization trying to voyage across the galaxy. Signaling – via radio, of course – was much easier and cheaper.

And that was it. The rest of the talk was on Radio SETI. Optical SETI might have had a mention or two, but back then it was just becoming acceptable by mainstream SETI long after being rejected following Charles Townes 1961 paper on the subject. The reasoning was that if humanity wasn’t up to sending powerful laser messages across the stars, then ETI wouldn’t either!

Thank goodness thinking is finally starting to change. The very recent launch of those StarChips predecessors, the Sprites, is even waking people up to the possibility that ETI could send very small probes to study other worlds, including us. The idea was brought up decades ago, but this is what happens when a field is dominated by just one specialty, in SETI’s case radio astronomers.

Great essay again, Mr. Nielsen!
And great comments, and I like following after Robert G., with whom I again fully agree, as in the previous METI discussion.

I was somewhat saddened by all the ‘impossibility of interstellar travel’ talk, even by distinguished scientists, but I was encouraged by the mentioning of A.C. Clarke, because I was reminded of his 1st Law. In fact, all his 3 Laws apply here, and I would like to mention them:
1) When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2) The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
3) Any sufficiently advanced technology is indistinguishable from magic.

Further to Robert G. and the idea of some kind of hibernation/cryonics as a solution for human interstellar travel, I can imagine a sort of ‘intermediate’ interstellar travel solution, in which not entire humans are sent, but human egg and sperm cells, or fertilized eggs (zygotes). Those are the absolute minimum to which a human being can be reduced, while still containing all the information.
We could think of even further reaching and more fantastic reductions, such as sending purely DNA codes, to be bio-assembled at destination, but there may not be much if any gain in this, and much unneccesarily added complexity and risk. The cell is a very neat and compact biological information package, since billions of years, so why not utilize it?!
Of course, the offspring would have to be raised by intelligent robots, which poses its own risks and challenges.

James P. Hogan’s novel Voyage from Yesteryear is about human children, brought as eggs to another planetary system, raised by robots.

The options we have for “slow” interstellar travel are few and familiar:

1. a generational starship with a living population of sufficient size to be genetically viable over the time scale of the voyage
2. transport of passengers in some kind of hibernation or stasis
3. transport of passengers in the form of frozen eggs or embryos
4. transportation of genetic information that is then reconstituted at destination by automated means
5. the kind of planet-hopping that I describe above
6. the use of a Shkadov thruster or some other kind of stellar engine to move an entire star and its planetary system

Am I forgetting anything?

It is worth noting that these methods are not mutually exclusive, and that they could be employed in combination. By combining multiple means, even a relatively “low” technology civilization might aspire to intergalactic travel.

Regarding the Clarke novel, The City and the Stars, it would be good to remember that in the billion year old city of Diaspar, only one man is actually human, Alvin…no last name either…Not even his parents were human…The central computer evidently can put together what is required for human reproduction…

In Diaspar, the entire city is run by the Central Computer. Not only is the city repaired by machines, but the people themselves are created by the machines as well. The computer creates electric bodies for the people of Diaspar to live in and stores their minds in its memory at the end of their lives. At any time, only a small number of these people are actually living in Diaspar; the rest are retained in the computer’s memory banks. But remember people in the story only seem to be human…they are not human…they are creations by the computer…only Alvin is actually human…and he is very curious to find a way out of the city…

This might be stagnation on an immense scale…no exploration for a billion years…no human reproduction…no cry for contact with other creatures…I can’t even recall seeing a cat or a dog in Diaspar…

This would be a most extreme case for the regeneration of a species that had lost its way…because Alvin finds a way out of the electric city and into a neighboring city of real people…thank goodness…

I think that the most powerful driver for colonization in this case, is finding a nearby planetary system that is almost identical in its life-supporting qualities as one’s home world.

In our case, I’d say that the discovery of an “Earth 2.0” in the AC system would be a powerful driver for space colonization development, since policymakers would be able to see a return on investment. This may be extremely rare; what would happen if we surveyed the entire AC system and found lots of planets, with different kinds of life, yet nothing that could support humans?

We might assume that other “civilizations” would be constrained in similar fashion.

It’s interesting to see an entomologist weigh in on this question. Insect colonies could be regarded as another model of “civilization”; would interstellar technology be something to be evolved organically?

It would no doubt be a great stimulation to the human imagination and to our ambitions for exploration if we determined that a relatively nearby world had a biosphere. The likelihood of any biosphere in another planetary system being, “almost identical in its life-supporting qualities as one’s home world,” is close to zero. Given the rate at which life speciates when separated on Earth (allopatric speciation), life separated across interstellar distances, even if related by distant panspermia, would have traveled a very different path. So the possibility of a biosphere that can support human life (without terraforming) is extremely low. Nevertheless, other biospheres would be of great scientific interest to us.

Civilizations expand for all kinds of reasons, not just settlement: conquest, trade, intellectual curiosity, and proselytization, among them. Perhaps some of these motivations support an ongoing effort of significant magnitude better than others, and long lasting or expanding civilizations will be selected for the most effective motivations for projects of a cosmological scale.

Quote by J. N. Nielsen: “We may never get to the point when we can put quantum theory and general relativity together, and the technology to control gravity would remain beyond our ability.” This is true only by the limitations of today’s technology. I think that physicists will agree that it is a common misconception or opinion that we can’t combine general relativity and quantum field theory. These have already been combined to a certain extent for example: the geodesics of the path of particles through space and time are already part of the equations of quantum electrodynamics, chromodynamics etc.
The graviton has to be handled differently since the standard model is not background independent but general relativity is background independent. A quantum theory of gravity is not perturbatively renormalizable. The graviton, Wikipedia. We have discovered gravity waves which are a form of energy and any form of energy can be manipulated. A gravitational wave rocket would still be relativistic or subluminal. A warp drive needs negative energy density to work.

Scientific knowledge will never stagnate though at least not indefinitely since scientists will always look to build a better mousetrap or try and refine and make a technology more efficient. There could be both periods or cycles of stagnation and progress after breakthroughs but there will always be scientists and the need to break barriers and limitations. There will always be a scientists who think they can solve a technological problem since the archetype of Prometheus represents the creative mind, progress ingenuity and inventiveness and a scientific zeitgeist which isn’t always opposed to an economic, material zeitgeist.

Very interesting article on civilizations on the grand scale of time and space—stagnant civilizations that succeed in colonizing passing stars, but leave a very slight “cosmic footprint” are definitely food for thought.

It reminds me of John W. Campbell’s The Black Star Passes—which was the first appearance of this form of interstellar travel in SF. Actually it, is was also the last to my knowledge. Does anyone know if SF writers have used this kind of interstellar travel in fiction since?

Yes, interstellar travel is impossible for us, located in a diffusely populated arm of our spiral galaxy, but it might be possible for civilizations located in regions of the galaxy where stars are more closely spaced (such as galactic centers, globular clusters, or merely closely-packed regions of elliptical galaxies).

Playing devil’s advocate here, I was given to understand that those densely packed regions of space where probably not the best locations for habitable planets and life? Passing stars can gravitationally disrupt planetary orbits, and in the galactic center, supernovae are quite common. Higher levels of radiation would be even more inconvenient for spacefarers who venture outside their home planet’s protective atmosphere and magnetosphere. Stars in globular clusters tend to have low metallicity, as well.

Some have gone so far as to suggest there is a “Galactic Habitable Zone” (GHZ) circumscribing the Milky Way at a fair distance from the center. Earth, naturally, is in this zone. If there really is a GHZ, civilizations will tend to form in regions similar to ours, with the stars fairly far away.

I wasn’t aware of the paper you cite on civilizations in globular clusters. It puts life in globulars in a different light, but I’m still wondering about the galactic center. A region densely packed with hot, short-lived O-type stars and frequent supernovae doesn’t seem the healthiest place for civilizations to develop.

It has been a commonplace for some time that the centers of spiral galaxies are not good places for life or civilization. This is likely true, but it is also likely that there are regions within spiral galaxies where stars are more densely packed and conditions are reasonably favorable to life. The galaxy is a big place, and there are probably anomalous habitable zones hidden here and there.

Globular clusters are also not very amenable to life and civilization, as the processes of galactic ecology that occur in spiral and elliptical galaxies do not occur in globular clusters, so when R. Di Stefano and A. Ray published their paper they were definitely swimming against the tide. I don’t think that civilizations are likely in globular clusters, but I certainly won’t say that they are impossible.

If terrestrial civilization embodies the principle of mediocrity, that does not rule out the possibility of exceptional civilizations coming into existence in exceptional circumstances, but it does imply the unlikelihood of such civilizations. Thus if civilization is common in the universe, we would expect to see a distribution of civilizations with most occupying the bump in the bell curve of habitability, and fewer civilizations on each side of the bump. But if civilizations are rare, perhaps we only find them where conditions for life are just right, and unlikelihood is sufficient to prevent exceptional civilizations from evolving.

Small groups of human beings have lived and thrived in isolated environments for thousands of years , even without a helping hand from modern technology .
On islands in the pacific Ocean and several other cut-off places , people have build smal self-sustaining comunities that would last until something broke the isolation .
So , why is it that this ‘elefant in the room’ is completely transparent to most people in this discussion ? …and even more so for the total deniers of space travel ?
The stars can be reached in manny different ways , but the most simple and effective one is not to be mentioned…..because it involves re-designing our selves and our social structures into something that can live with the same kind of hardship and suffering that our ancestors took as the natural way of things .
Do you think they were more stupid than we are ?
The REAL answer to the ‘Seti-Paradigm’ is to say aloud that people wil reach the stars No Matter What .
Perhabs it will be on first class , but more likely it wil be on a 2000 year long voyage involving endless suffering which can only be endured while centering life around family , tradition and the hard work neccesary to keep the starship alive and well …much like a tribe of cave-men surviving the ice age

The nuclear weapons tests of the 50’s and 60’s prove that inertial confinement fusion works when given enough scale. So a Daedalus type pulse fusion drive is a mere engineering challenge. You just need a big enough bucket with enough free electron lasers to fuse the pellets.

Such a craft would be expensive. But Lofstrom loops and orbital rings can give us access to all the planetary and sub planetary resources for us to grow in to. Centrifugal space habitats can provide many times the living space of Earth and make homes for a growing population of trillions.

So when exponential growth begins to exhaust all the construction materials available in the solar system it would make sense that at least some of them would groups would invest the resources to send there habitats and stockpiles of to another solar system so they can continue growing. People do care about the fate of their grand children but life extension would make such long term projects such as a generation ship even more attractive.

I think the answer to Fermi’s paradox is the difficulty of abiogenisys. The universe is full of lifeless sterile worlds waiting for humans to spread the seed of life.

Orbital rings and Lofstrom loops are more useful than space elevators and don’t require new super materials to build I think it a shame the space elevator is the better known idea.

A ground launched Orion drive produces less fall out than many of the other atmospheric nuclear tests. We could of built an interstellar ship half a century ago if we had wanted to.

Some of the best sci-fi novels I’ve read used stagnant super-civilization as a theme. Most notable is Asimov’s Foundation trilogy, which describes the stagnation and gradual fall of a galaxy-wide empire, and the founding of a new society to shorten the interregnum. Dune addresses it more subtly, but it’s there if you read through — the feudal system of Emperor/Great Houses/Guild/CHOAM/etc. is stagnant, and the “Golden Path” is about breaking this stagnation. The Scattering prevents humanity from being homogenized/centralized, and there’s a parallel between this and traveling to other stars in reality. God Emperor of Dune presents a vision in which “hunter-seeker” machines with self-improving AI would run rampant and exterminate our species, which was prevented by the aforementioned Golden Path. In any case, there are plenty of historical examples of stagnation to draw from, and I don’t think future developments will eliminate that particular pitfall.

Given the speed of light, astronomical distances, and engineering requirements, space travel is difficult, but not impossible. With better technology and infrastructure, it will come within our reach. 300 years ago, who would’ve believed that a man-made craft could fly around the world within a week? But with new technology, infrastructure and economy, it has become a reality. Likewise, there is no reason why interstellar flight and colonization cannot become a reality in the future. It is true that c imposes a hard limit, but I see this as positive, as it would prevent homogenization and enforce relative distance.

I doubt we are the only instance of civilization. Given the huge number of galaxies, and potential solar systems within galaxies, it is probable that there is life and civilization out there, although it is hard to guess at its abundance. There may be an advanced civilization elsewhere in the Milky Way, perhaps on the opposite side of the core. As I’ve said on here before, there is no reason to assume that an alien civilization must be contemporary. It is possible that our first contact with ETI will be in the form of abandoned ruins and artifacts.

Beyond the topic at hand, what’s particularly striking about The Farthest is the number of women who worked on it. I ask Reynolds about this, and how it may tie into the recent moves by the Irish Film Board to address gender imbalance in Ireland’s film industry.

“It’s wonderful now to see, the change is so positive and it’s so dynamic. And it’s a real turning of the wheel, which I really applaud,” says Reynolds of the deliberate steps to bring about gender parity. Over the years she worked as a film editor, just a “minuscule fraction” of the directors she worked with were women.

“Encouraging women into key positions is fantastic for everyone,” she says. The film itself reflects that.

“We took it as read that women’s voices would be loud and proud in it,” says Reynolds. This also reflects the growth in acknowledgement of women’s role in scientific discoveries, such as the film Hidden Figures.

After the documentary was shown at the Audi Dublin International Film Festival, Reynolds got three letters from young girls (two aged 10 and one aged 12) telling her they want to be scientists.

“I was like, ‘my work is done’,” says Reynolds. “That was the thrill of a lifetime, for me to inspire them.”

Interestingly, the Voyager crew have mixed feelings about the famous “golden record” that each craft carries. This is a gold-plated copper LP, packed with a needle, cartridge and instructions, and containing, in groove form, photos from Earth, a selection of natural sounds, plus music from a variety of cultures and eras. Tracks include Chuck Berry’s Johnny B Goode, Glenn Gould performing from Bach’s Well-Tempered Clavier, and a pygmy girl’s initiation song from Zaire.

Carl Sagan, the project supervisor and astrophysicist, had wanted to include The Beatles’ Here Comes the Sun, but EMI turned him down, saying “We don’t licence for outer space.” There are, additionally, spoken greetings in 55 languages, including such ancient dialects as Akkadian and Hittite. The Amoy message asks: “Friends of space, how are you all? Have you eaten yet? Come visit us if you have time.” Nick Sagan, the Star Trek writer and son of Carl Sagan, recorded the English message as a child: “Hello from the children of planet Earth.”

“I think one of the great things about Voyager is that it just naturally has these two pieces to it,” says Reynolds. “The heart and the mind. It combines extraordinary scientific discoveries and achievement with this romantic attempt to describe how we are as humans to an extra-terrestrial audience. This little craft built in the 1970s is knocking it out of the park in terms of science. But it also has this amazing golden record attached to the outside of the craft which is insane that is trying to communicate with aliens. It has everything we are as people.”

If a civilization uploads itself into a computer, could it be called stagnant? Setting the clock-speed to run so people experience time at 10^20 times normal would mean doing anything in the real world would take a near eternity. Would such a people even bother with reality?

As for exploration, even travelling a mere 3 milimeters would take a billion years of simulated time, though zero time for the traveller. Would a person interested in exploration bother looking outside the simulation when they got a near infinite number of worlds and people to explore that doesn’t risk their death? Even that short distance of 3 milimeters means they could never return to their own civilization which would have been dust for billions of years.

They might never get beyond their own homeworld, but trillions of civilization, each with population greater than that of a whole galaxy of dyson swarms, could rise and fall within such a simulation every day.

Once again, this is a lot like John Smart’s transcension hypothesis, which I mentioned above in my response to Dimjo’s comment (above). Why would any civilization choose to do things in the real world when virtual worlds could be scaled in the way you suggest?

This is an interesting position, but I don’t think it’s the final word. Ultimately, this is a question about the ongoing relevance of human life as we know it. I haven’t yet addressed this in a systematic way. I believe that human beings will remain relevant to terrestrial civilization for a long time to come, but I won’t try to make the argument here.

Some things to consider:

1. We don’t know that consciousness can scale in virtual environments. I.e., you might not be able to advance the clock speed much beyond that of the human nervous system and still have consciousness function as it does. There may be other forms of awareness, distinct from human consciousness, which can be scaled in virtual environments, but we can’t test this idea until we have virtual environments consisting of multiple instances of consciousness.

2. If a civilization should focus on virtuality but remain tightly-coupled to its homeworld, it is subject to existential risks that it would be able to mitigate by distributing itself more widely in the non-virtual world. Even something as powerful as a matrioshka brain couldn’t protect itself from cosmological scale accidents if it exists in one place only. Also, something like this would not survive its host star growing into a red giant.

3. An ideal virtual environment with “a near infinite number of worlds and people to explore that doesn’t risk their death” would become boring after a while. If there are no real world consequences of one’s actions, these actions come to be seen in a different light. I addressed this above in my discussion of the pursuit of “limit experiences.” It would be a fun exercise (perhaps this could be the basis of a future post on the simulation hypothesis, the transcension hypothesis, and related ideas) to compare these virtual world exercises and their presumed outcomes to what Nietzsche called the “Last Men.” (For the time being you can see what I wrote about the “Last Civilization.” https://geopolicraticus.wordpress.com/2011/02/10/the-last-civilization/)

If a species responds on average slightly more aggressively to the prisoners dilemma, they may not be able to last more than a couple of decades nuclear stand off. But if you have nukes you can also build interstellar ships with Orion Drive so being more cavalier with radiation their space race involved ground launching Orion Drive powered generation ships as insurance before destroying most of their industry in nuclear war. They have enough tools on their generation ships to build habitats and other generation ships from asteroids but their fear of mutually assured destruction lead to rival factions always fleeing or destroying each over. So they they never get the economies of scale required for true microchip fabrication, for them it is forever the 60’s. This is an almost plausible way to have the sci-fi trope of a defeatable alien invader if you postulate that modern human civilisation only came out of the Cold War without it going hot was because humans are irrationally and exceptionally optimistic in prisoner’s dilemma situations. Maybe even plausibly have some scattered remains of a brief stay in our asteroid belt before rival factions destroyed each other with any survivors fleeing. Remember an Orion drive can always double as a nuclear machine gun.

Another is that if a new understanding of the “EM Drive” anomaly produced a cheap and easy to manufacture warp drive. Then when everyone’s car can fly round the world within an hour, everyone has a delivery vehicle faster and more manueverable than a balistic missile. Borders and border walls become useless, all national governments collapse due to tax evasion by those international commuters. Somali pirates can now raid any suburb on the planet. Billions of poor wannabe pirates can pop out of any sky at any moment and try to capture you for the ransom money or worse. The only way most people have to hide from the pirate plague is to disperse amongst the billions of planets in the galaxy. Any trading post that becomes a known location to too many people is vulnerable to piratical warp ships popping out of the sky at any moment. So we get warp drive but due to lack of economies of scale everything else becomes more primitive. And the population density of the galaxy is kept low by predation from pirates and slavers.﻿

Well, some new physics is needed to put it all together. That new physics may well be string theory in a later iteration, and when the technology is available to make it testable and therefore empirically applicable. This, if it happens, represents a civilization converging upon scientific maturity (having a complete and adequate physical theory). Also being able to apply the results of scientific maturity to to implementable technologies is another matter. However, it occurs to me only now as I write this that a civilization that must push the limits in order to keep its most advanced science testable would also be a civilization developing new technologies capable of such testing. This implies some kind of virtuous circle of development, like the STEM cycle I have described in previous Centauri Dreams posts, but at another level. This is an idea worth pursuing, so I will continue to think about it, but I don’t see the immediate relevance to anthropogenic limits to interstellar travel.

This is precisely why I consider stagnation to be a clear and present danger, as existential risks go, especially in comparison to the possibility of unfriendly AI, which is still entirely speculative.

“The Pioneer plaques are destined to be the longest-lived works of mankind,” said Sagan and Drake in 1975. “They will survive virtually unchanged for hundreds of millions, perhaps billions, of years in space. When plate tectonics has completely rearranged the continents, when all the present landforms on the earth have been ground down, when civilization has been profoundly transformed and when human beings may have evolved into some other type of organism, these plaques will still exist. They will show that in the year we called 1973 there were organisms, portrayed on the plaques, that cared enough about their place in the hierarchy of all intelligent beings to share knowledge about themselves with others.”

The universe is incomprehensibly vast, with billions of other planets circling billions of other stars. The potential for intelligent life to exist somewhere out there should be enormous.

So, where is everybody?

That’s the Fermi paradox in a nutshell. Daniel Whitmire, a retired astrophysicist who teaches mathematics at the University of Arkansas, once thought the cosmic silence indicated we as a species lagged far behind.

“I taught astronomy for 37 years,” said Whitmire. “I used to tell my students that by statistics, we have to be the dumbest guys in the galaxy. After all we have only been technological for about 100 years while other civilizations could be more technologically advanced than us by millions or billions of years.”

Recently, however, he’s changed his mind. By applying a statistical concept called the principle of mediocrity – the idea that in the absence of any evidence to the contrary we should consider ourselves typical, rather than atypical – Whitmire has concluded that instead of lagging behind, our species may be average. That’s not good news.

In a paper published Aug. 3 in the International Journal of Astrobiology, Whitmire argues that if we are typical, it follows that species such as ours go extinct soon after attaining technological knowledge. (The paper is also available on Whitmire’s website.)

You mention expanding into the Oort Cloud and Kuiper Belt, but we can also consider widely spaced multiple star systems, whose members are presumably permanently bound (though not necessarily.)
One example is Iota Librae, two pairs of stars; the two pairs are almost 7000 AUs apart. I wonder what the distribution of asteroid and comet belts would be like?
And will civilizations there be encouraged to migrate to nearby systems?

We discuss how visions for the futures of humanity in space and SETI are intertwined, and are shaped by prior work in the fields and by science fiction. This appears in the language used in the fields, and in the sometimes implicit assumptions made in discussions of them. We give examples from articulations of the so-called Fermi Paradox, discussions of the settlement of the Solar System (in the near future) and the Galaxy (in the far future), and METI.

We argue that science fiction, especially the campy variety, is a significant contributor to the “giggle factor” that hinders serious discussion and funding for SETI and Solar System settlement projects. We argue that humanity’s long-term future in space will be shaped by our short-term visions for who goes there and how. Because of the way they entered the fields, we recommend avoiding the term “colony” and its cognates when discussing the settlement of space, as well as other terms with similar pedigrees.

We offer examples of science fiction and other writing that broaden and challenge our visions of human futures in space and SETI. In an appendix, we use an analogy with the well-funded and relatively uncontroversial searches for the dark matter particle to argue that SETI’s lack of funding in the national science portfolio is primarily a problem of perception, not inherent merit.

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last twelve years, this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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